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CONCLUSIONS AND RECOMMENDATIONS <br /> In summary, the soil conditions examined near the proposed septic system drain field <br /> were found to be suitable for a standard septic system. A satisfactory soil percolation <br /> rate of 10 min/in was observed in the deep (six-foot) soil zone at the test location. The <br /> soil in the test location was found to be silty/sandy clay. <br /> The depth of ground water based on recent aquifer levels is approximately 103 to 130 <br /> feet below ground surface. Ground water flows to the northwest in the area at a rate of <br /> approximately six to nine feet per mile. <br /> Because of the percolation rate between 5.0 and 30.0 min/in encountered in the test <br /> hole, the San Joaquin County Environmental Health Department will require an eight- <br /> foot separation from the bottom of the dispersal system to ground water. Based on the <br /> anticipated depth to ground water, no modifications to standard septic systems should <br /> be required. <br /> A water sample was collected from the domestic well on the Site as part of this <br /> investigation. Nitrate was detected in the sample at a concentration of 0.2 mg/L-N, well <br /> below the MCL of 10 mg/L-N. No DBCP was detected in the sample. <br /> Based on the methods and assumptions described, the nitrate loading calculation <br /> indicates that the use of on-site septic tanks and drain field systems on the Site has the <br /> potential to cause a buildup of nitrate in the aquifer up to 9.5 mg/L, below the MCL of 10 <br /> mg/L-N. <br /> Septic system construction utilizing leach lines and seepage pits should follow the San <br /> Joaquin County On-Site Wastewater Treatment Systems Standards (2017) where <br /> applicable. Based on the results of the nitrate loading analysis, no nitrate mitigation is <br /> recommended. <br /> LOGE 20-31 Page 13 <br />